Once.again,I.would.like.to.share.Harry.Francis'.comments.on.the.longevity.of.
whitewash:

As to Whitewash, and effective lifetime... On the inside cover of the NLA
Whitewash brochure --I think, no longer available---- was a picture of
a masonry home in the Washington DC area - using the white wash formula
utilizing salt, casine, formaldehyde and TSP (If I remember correctly)....that
was still satisfactory after 35 years........ I understand the home has
now been destroyed....

Generally whitewash is thought of as a sacrificial agent --protecting the
underlayer, and should be renewed as necessary.

Whitewash made with casine forms a glue, but this
is water soluble.....so adding a little rosin oil or other oils makes it
water proof.....

I think the answer to long lasting white wash is to apply it pretty
thin---transluscent,
when applied. Let dry, then apply additional coats to get the coverage
you desire, letting each coat dry between applications. If you try to do
a thick one coat application, the material drys, cracks and peels.
At least that has been my experience.

Harry

The.last.whitewash.project.we.were.involved.in.(Cliveden-of-the-National-Trust
)used.a.simple.slaked.lime/salt.mix.(I.would.have.to.look.up.the.proportions).
...It.has.held.up.almost.5.years,but,in.some.places,has.developed.a.brown.stai
n...The.stains.seem.internal-moisture-related,but.haven't.been.able.to.see.a.p
attern.as.to.why.
the.wall.would.be.wet.at.those.locations???

John.Mascaro